1. Field of the Invention
The present invention relates to a disc reproducing apparatus suitable for use as a CD-ROM player as well as to a magnetic disc recording/reproducing apparatus.
2. Description of the Prior Art
Today, typical CD-ROM players have a constant linear velocity of 1.2 to 1.4 m/s and a reproduction data rate of 1.8816 Mb/s. However, the reproduction data rate of 1.8816 Mb/s of the CD-ROM player is not high enough to record animation data and the like adequately. What is needed is to raise the reproduction data rate without changing the pit lengths on the compact disc serving as the CD-ROM. If the linear velocity of the CD-ROM compact disc is doubled to 2.4 to 2.8 m/s, the data rate is also doubled. One way to implement this is to have the compact disc comprise two areas of different data rates: one having a reproduction data rate of 3.7632 Mb/s (i.e., double the normal rate) for animation data and the like, the other having the normal data rate. The revolutions of the spindle that rotates the compact disc are controlled according to the area so that the line velocity is changed where needed. This scheme makes it possible to retrieve from the compact disc the data such as animation data to be reproduced at the higher bit rate.
One disadvantage of the above-described scheme is that when the line velocity is changed so as to alter the reproduction data rate, the data cannot thereupon be reproduced until after the servo mechanism is stabilized.